The present invention relates to new substituted campositions derivatives possessing antitumor activity, to a process for their preparation, and to pharmaceutical compositions containing them.
Campcothecin and some of its analogs display potent antitumor activity by the inhibition of Topoisomerase I, that is an enzyme involved in some important cellular functions and cellular growth (see, or instance, Wanl et al., J. Med. Chem. 1987, 30, 1774; Hsiang et al., Cancer Res. 1998, 49, 4385; Cancer Res. 1989, 49, 1465) Anitcancer activity of Camptothecin both in vitro and in vivo is significantly greater for the lactone versus the carboxylate form has disclosed, for instance, by W. J. Slichenmyer et al., in xe2x80x9cThe Current Status of Camptothecin Analogues as Antitumor Agentsxe2x80x9d, J. Natl. Cancer Inst. 1993, 85, 271-291, and references therein), since a closed xcex1-hydroxy Lactone ring is an important structural requirement for both passive diffusion of drug into cancer cells, as well as for successful drug interaction with the pharmacological target.
It has recently been pointed out that, the presence of biologically relevant levels of human albumin, the biologically active form of camptothecin has a very short half-life (about 12 min.), and 2 hours after drug addition to human plasma, a percentage greater than 99% of the drug has converted to camptothecin carboxylate, the biologically inactive and potentially toxic form of the drug (see Burke, G. T.; Mi, Z. xe2x80x9cThe Structural Basis of Camptothecin Interactions with Human Serum Albumin: Impact on Drug Stabilityxe2x80x9d, J. Med. Chem. 1994, 37, 40-46). The same authors disclose also the importance of the substitution in 9 and 7 positions on the camptothecin nucleus in order to improve drug stability in the presence of albumin.
There is therefore a need to find new camptothecin derivatives that have high intrinsic potency, and may gain, at the same time, stability in the presence of serum albumin.
Accordingly, the present invention relates to alkynyl-substituted camptothecins of formula (I) 
wherein:
R1 is selected from:
hydrogen;
an optionally substituted C1-C6 alkyl;
C3-C7 cycloalkyl;
C3-C7 cycloalkyl C1-C6 alkyl;
phenyl C1-C6 alkyl;
an optionally substituted phenyl;
an optionally substitued naphthyl;
xe2x80x94Rxxe2x80x94NR3R4, wherein Rx is C1-C4 alkylene, R3 and R4 are, each independently, hydrogen, C1-C6 alkyl, phenyl, or benzyl;
xe2x80x94(Ry)mxe2x80x94COOR5, wherein m is zero or 1, Ry is C1-C4 alkylene, R5 is hydrogen, C1-C6 alkyl, C3-C7 cycloalkyl, or phenyl C1-C6 alkyl;
xe2x80x94(Rz)nxe2x80x94COR6, wherein n is zero or 1, Rz is C1-C4 alkylene, R6 is C1-C6 alkyl, C1-C7 cycloalkyl, phenyl C1-C6 alkyl, an optionally substituted phenyl, or xe2x80x94NR7R8, wherein R7 and R8 are, each independently, hydrogen or C1-C6 alkyl; and
xe2x80x94SiR9R10R11, wherein R9, R10 and R11 are, each independently, C1-C4 alkyl;
R2 is selected from:
hydrogen.; C1-C6 alkyl; C2-C7 cycloalkyl; and phenyl C1-C6 alkyl;
X Is selected from:
hydrogen; C1-C6 alkyl; C1C7 cycloalkyl; C1C6 alkoxy; C3-C7 cycloalkoxy; C1-C6 alkanoyloxy; benzoyloxy; amino; hydroxy, nitro; chlorine; and a methylene- or ethylene-dioxy group linked to positions 10 and 11 of the molecule;
and the pharmaceutically acceptable salts thereof.
In the formulae of the present specification, a dotted line () indicates a substituent below the plane of the ring, while a wedged line () indicates a substituent above the plane of the ring.
Pharmaceutically acceptable salts according to the present invention are the salts with pharmaceutically acceptable acids, both inorganic acids such as, e.g. hydrochloric, sulfuric, phosphoric, diphosphoric, hydrobromic or nitric acid, and organic acids such as, e.g., citric, fumaric, maleic, malic, ascorbic, succinic, tartaric, benzoic, acetic, trifluoroacetic, methanesulfonic, ethanesulfonic, benzenesulfonic, or p-toluensulfonic acid.
Pharmaceutically acceptable salts of the compounds of formula (I) containing an acid group, i.e. carboxy, with pharmaceutically acceptable bases are also included in the scope of the present invention. Pharmaceutically acceptable bases may be both inorganic bases such as, for instance, alkali metal, e.g. sodium or potassium, or alkaline earth metal, e.g. calcium or magnesium, hydroxides, and organic bases such as, for instance, alkyl amines, e.g. methylamine or triethylamine, aralkylamines, e.g. benzylamine, dibenzylamine, xcex1- or xcex2-phenyl-ethylamine, or heterocyclic amines such as, e.g., piperidine, 1-methyl-piperidine, piperazine or morpholine.
An optionally substituted phenyl may be represented by a group 
wherein Q, linked to ortho, meta or para position of the phenyl ring, represents hydrogen, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 alkanoyloxy, nitro, amino, mono- or di-alkylamino with from 1 to 6 carbon atoms in the alkyl moiety, tolylsulfonylamino or chlorine, or Q represents a 5 or 6 membered aromatic heterocycle with one or two heteroatoms selected among nitrogen, oxygen or sulphur, optionally mono- or di-substituted by C1-C6 alkyl groups. Examples of the said heterocycles are, for instance, pyrrole, imidazole, pyrazole, isothiazole, isoxazole, furan, thiophene, pyridine, pyrazine, pyrimidine and the like.
Preferably, Q is hydrogen, C1-C4 alkyl, C1-C4 alkoxy, amino, tolylsulfonylamino, chlorine, or Q represents an optionally substituted pyrrole. Particularly preferred values of Q are hydrogen, methoxy, amino, tosylamino, 2,5-dimethylpyrrol-1-yl and chlorine.
An optionally substituted naphthyl is a naphth-1-yl or naphth-2-yl group optionally substituted by C1-C6 alkyl or alkoxy groups.
In the present specification, the hydrocarbon chain of the alkyl, alkylene, alkoxy, and alkanoyloxy groups may be a straight or branched chain.
Preferably, C1-C6 alkyl is C1-C4 alkyl, e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl or t-butyl. More preferably, C1-C4 alkyl is methyl, ethyl or propyl. The C1-C6 alkyl may be substituted, e.g., by hydroxy, alkoxy, phenoxy, thioalkyl, amino, or alkylamino groups.
Preferably, C3-C7 cycloalkyl is C4-C6 cycloalkyl, e.g. cyclobutyl, cyclopentyl or cyclohexyl.
Preferably, C3-C7 cycloalkyl C1-C6 alkyl is cyclopentylmethyl, cyclohexylmethyl, 2-cyclopentylethyl, 2-cyclohexylethyl, 3-cyclopentylpropyl or 3-cyclohexylpropyl.
Preferably, C1-C4 alkylene is, e.g., methylene, ethylene, n-propylene, 1-methyl-ethylene, n-butylene, 1-dimethyl-ethylene, 1,2-dimethyl-ethylene, or 1-methyl-propylene.
Preferably, C1-C6 alkoxy is C1-C4 alkoxy, e.g. Methoxy, ethoxy or propoxy.
Preferably, C1-C6 alkanoyloxy is C1-C4 alkanoyloxy, e.g. methanoyloxy, ethanoyloxy or propanoyloxy.
A preferred class of compounds according to this invention is represented by compounds of the above formula (I) wherein:
R1 is selected from:
hydrogen; C1-C4 alkyl; phenyl C1-C6 alkyl; phenyl; xe2x80x94Rxxe2x80x94NR3R4, wherein Rx is a C1-C4 alkylene, R1 and R4 are, each independently, C1-C4 alkyl; xe2x80x94(Ry)mxe2x80x94COOR5, wherein m is zero or 1, Ry is a C1-C4 alkylene, R9 is hydrogen or C1-C4 alkyl; and xe2x80x94(Rz)nxe2x80x94COR6, wherein n is zero or 1, Rz is a C1-C4 alkylene, R6 is C1-C6alkyl, phenyl, or xe2x80x94NR7R8, wherein R7, and R8 are hydrogen; and xe2x80x94SiR9R10R11, wherein R9, R10 and R11 are methyl or ethyl;
R2 hydrogen or C1-C4 alkyl;
X is selected from:
hydrogen; amino; hydroxy; C1-C C6 alkoxy; or a methylene- or ethylene-dioxy group linked to positions 10 and 11 of the molecule;
and the pharmaceutically acceptable salts thereof.
Examples of specific compounds according to the present invention are the following:
9-ethynyl-camptothecin (1);
9-phenylethynyl-camptothecin (2);
9-(dimethylaminopropyn-1-yl)-camptothecin (3);
9-hydroxypropyn-1-yl-camptothecin (4);
9-trimethylsilylethynyl-camptothecin (5);
9-cyclopentylethynyl-camptothecin (6);
9-cyclohexylpropyn-1-yl-camptothecin (7);
9-hexyn-1-yl-camptothecin (8);
7-ethyl-9-ethynyl-camptothecin (9);
7-ethyl-9-phenylethynyl-camptothecin (10);
7-ethyl-9-(dimethylaminopropyn-1-yl)-camptothecin (11);
7-ethyl-9-hydroxypropyn-1-yl-camptothecin (12);
7-ethyl-9-trimethylsilylethynyl-camptothecin (13);
7-ethyl-9-cyclopentylethynyl-camptothecin (14);
7-ethyl-9-cyclohexylpropyn-1-yl-camptothecin (15);
7-ethyl-9-hexyn-1-yl-camptothecin (16);
9-(4-methoxyphenyl-ethynyl)-camptothecin (17);
9-(3-tosylamino-phenylethynyl)-camptothecin (18);
9-[3-(2,5-dimethyl-pyrrol-1-yl)phenylethynyl]-camptothecin (19);
9-(4-chlorophenyl-ethynyl)-camptothecin (20);
9-(N-benzyl-N-methylamino-propyn-1-yl)-camptothecin (21);
9-(5-phenyl-pentyn-1-yl)-camptothecin (22);
9-(3-phenoxy-propyn-1-yl)-camptothecin (23);
9-[(6-methoxy-naphth-2-yl)-ethynyl]-camptothecin (24);
9-(3-hydroxy-3-methyl-butyn-1-yl)-camptothecin (25);
9-(3-methoxy-propyn-1-yl)-camptothecin (26);
9-(diethylamino-propyn-1-yl)-camptothecin (27);
9-(methylamino-propyn-1-yl)-camptothecin (28);
9-(3,3-dimethyl-butyn-1-yl)-camptothecin (29);
9-(3-aminophenyl-ethynyl)-camptothecin (30);
10-ethynyl-camptothecin (31);
10-phenylethynyl-camptothecin (32);
10-(dimethylamino-propyn-1-yl)-camptothecin (33);
10-hydroxypropyn-1-yl-camptothecin (34);
10-trimethylsilylethynyl-camptothecin (35);
10-cyclopentylethynyl-camptothecin (36);
10-cyclohexylpropyn-1-yl-camptothecin (37);
10-hexyn-1-yl-camptothecin (38);
7-ethyl-10-ethynyl-camptothecin (39);
7-ethyl-10-phenylethynyl-camptothecin (40);
7-ethyl-10-dimethylamino-propyn-1-yl-camptothecin (41);
7-ethyl-10-hydroxypropyn-1-yl-camptothecin (42);
7-ethyl-10-trimethylsilylethynyl-camptothecin (43);
7-ethyl-10-cyclopentylethynyl-camptothecin (44);
7-ethyl-10-cyclohexylpropyn-1-yl-camptothecin (45);
7-ethyl-10-hexyn-1-yl-camptothecin (46);
and, where a salifiable substituent is present on the molecule framework, their pharmaceutically acceptable salts.
With reference to the above formula (I), the structural formulae of the above listed compounds are reported in the following Tables 1 and 2.
In Tables 1 and 2, the symbols Et, Ph, Bz and Ts stand for ethyl, phenyl, benzyl and tosyl, respectively, the symbols m and p stand for meta and para substituent onto phenyl ring, respectively.
The present invention relates also to a process for preparing the compounds of formula (I) as defined above, said process comprising:
(a) reacting a compound of formula (II) 
xe2x80x83wherein:
R12 is selected from: a halogen atom; a group xe2x80x94OSO2R13 wherein R13 is C1-C5 alkyl, optionally substituted at the terminal carbon atom by one, two or three halogen atoms; and an optionally substituted phenyl; ring;
R2 is selected from: hydrogen; C1-C6 alkyl; C3-C7 cycloalkyl; and phenyl C1-C6 alkyl; and
X is selected from: hydrogen; C1-C6 alkyl; C3-C7 cycloalkyl; C1-C6 alkoxy; C3-C7 cycloalkoxy; C1-C6 alkanoyloxy; benzoyloxy; amino; hydroxy; nitro; chlorine; and a methylene- or ethylene-dioxy group linked to positions 10 and 11 of the molecule;
xe2x80x83with a compound of formula (III): 
wherein Rxe2x80x21 is selected from:
an optionally substituted C1-C6 alkyl; C3-C7 cycloalkyl; C3-C7 cycloalkyl C1-C6 alkyl; phenyl C1-C6 alkyl; an optionally substituted phenyl; an optionally substituted naphthyl; xe2x80x94Rxxe2x80x94NR3R4, wherein Rx is C1-C4 alkylene, R3 and R4 are, each independently, hydrogen, C1-C6 alkyl, phenyl, or benzyl; xe2x80x94(Ry)mxe2x80x94COOR5, wherein m is zero or 1, Ry is C1-C4 alkylene, R5 is hydrogen, C1-C6 alkyl, C3-C7 cycloalkyl, or phenyl C1-C6 alkyl; xe2x80x94(Rz)nxe2x80x94COR6, wherein n is zero or 1, Rz is C1-C4 alkylene, R6 is C1-C6 alkyl, C3-C7 cycloalkyl, phenyl C1-C6 alkyl, an optionally substituted phenyl, or xe2x80x94NR7R8, wherein R7 and R8 are, each independently, hydrogen or C1-C6 alkyl; and
xe2x80x94SiR9R10R11, wherein R9, R10and R11 are, each independently, C1-C4 alkyl;
xe2x80x83so obtaining the corresponding compound of formula (I) and
(b) when Rxe2x80x21 is xe2x80x94SiR9R10R11, optionally removing the xe2x80x94SiR9R10R11 group by acid treatment so obtaining the corresponding compound of formula (I) having R1 equal to hydrogen; and
(c) if necessary, converting the so obtained compound of formula (I) into a pharmaceutically acceptable salt thereof.
The starting compounds of formula (II) have a 20(S)-configuration which is retained through the process leading to the compounds of formula (I). The compounds of formula (II) are typically free of the corresponding 20(R)-isomers However, said process may be applied to a racemic mixture of a compound or formula (II) and the corresponding 20(R)-isomer. In that case, a racemic mixture of a compound of formula (I) and a 20(R)-isomer of a compound of formula (I) is obtained.
When one or more new stereogenic centers are present in R1, all the possible isomers, diastereoisomers, epimers, and geometric isomers, are included in the present disclosure.
The reaction of step (a) may be performed in a suitable solvent, in the presence of catalytic amounts, i.e. from 0.0001 to 0.2 molar equivalents, of a compound of formula
MLqLxe2x80x2r
wherein:
M is a transition metal, preferably palladium, nickel or platinum;
L and Lxe2x80x2, which may be the same or different from each other, are anions, such as, e.g. halide or acetate, or neutral molecules, such as, e.g., solvent molecules, phosphines, phosphites or diamines; and
q and r are numbers from 0 to 4;
provided that q+r is at least 1.
The reaction of step (a) may be optionally carried out in the presence of a Cu(I) compound as co-catalyst, such as, e.g., a Cu(I) halide, CU2O, CuCN, or a CuCNxe2x80x94LiCl complex, preferably CuI, CuCl, or Cu2O.
The reaction temperature is generally from about xe2x88x9220xc2x0 C. to about 200xc2x0 C. preferably from about 20xc2x0 C. to about 100xc2x0 C. while the reaction time may vary from a few minutes to several days, such as, e.g., from 5 minutes to 3 days, preferably from about one hour to about one day. The reaction may be optionally carried out in the presence of a suitable organic or inorganic base, and of a lithium halide, such as, e.g., LiCl or LiBr.
Suitable solvents for step (a) may be, e.g., dimethylformamide (DMF), acetonitrile, dimethylsulphoxide (DMSO), CHCl3, dioxane, tetrahydrofuran (THF), or mixtures thereof. Suitable inorganic bases include, e.g., alkali or alkaline-earth metal salts, such as, for example, NaHCO3, Na2CO3, or NaOAc. Suitable organic bases may be, for example, trialkyalmines, such as, e.g., triethylamine or diisopropylethylamine; or heteroaromatic bases such as, e.g., pyridine, or 2,6-di-C1-C6 alkyl-substituted pyridines, such as, e.g., 2,6-lutidine. L and Lxe2x80x2 may be, e.g., halides; acetates; phosphines, such as, e.g., triphenylphosphine or chelating diphosphines, such as, e.g., bis(diphenylphosphino)methane, 1,2- and 1,3-bis(diphenyl phosphino)propane, 1,4-bis(diphenylphosphino)butane or 1,1xe2x80x2-bis(diphenylphosphino)ferrocene (DPPF).
The molar ratio between the transition metal and the ligands L and Lxe2x80x2 is generally from 1:1 to 1:4.
The reaction of optional step (b), wherein the xe2x80x94SiR9R10R11 group is removed by acid treatment so obtaining the corresponding compound of formula (I) having R1 equal to hydrogen, may be carried out with a suitable strong acid, e.g. trifluoroacetic acid.
The starting materials of formulas (II) and (III) are known compounds, or may be obtained following known methods. For instance, 9-halogen-, 10-halogen-, 11-halogeno-, and 12-halogeno-camptothecins may be prepared according, to Sawada, S. et al., Chem. Pharm. Bull. 39, 3183-3188 (1991).
For instance, 10-hydroxy-, 10-methoxy-, and 10,11-methylendioxy-9-halogen-camptothecins may be prepared starting from the corresponding 10- or 10,11-substituted-9-amino-derivatives, prepared by known procedures (see, for instance, Wall et al., J. Med. Chem. 36, 2689-2700, (1993), or Wani et al. J. Med. Chem. 29, 2358-2363, (1986)), and then following the above cited reference.
For instance, 9-trifluoromethansulfonyloxy camptothecin, 10-trifluoromethansulfonyloxy camptothecin, 10,11-trifluoromethansulfonyloxy camptothecin, 12-trifluoromethansulfonyloxy camptothecin, 10-hydroxy-9-trifluoromethansulfonyloxycamptothecin, 10-methoxy-9-trifluoromethansulfonyloxycamptothecin, 10, 11-methylendioxy-9-trifluoromethansulfonyloxy camptothecin, 10-p-toluensulfonyloxy camptothecin, 11-p-toluensulfonyloxy camptothecin, 12-p-toluensulfonyloxy camptothecin, 10-hydroxy-9-p-toluensulfonyloxy camptothecin, 10-methoxy-9-p-toluensulfonyloxy camptothecin and 10,11-methylendioxy-9-p-toluensulfonyloxy camptothecin, may be prepared from the corresponding hydroxy derivatives obtained, in turn, as described in the references cited above, by treatment with suitable sulfonylating agents.
Pharmacology
The compounds of the present invention are endowed with antitumor activity, for example against leukaemia and solid tumors such as, for example, colon and rectal tumors.
The antitumor activity of the compounds of the present invention is shown, for example, by the fact that they have been found to possess antileukaemic activity when tested according to the method described in J. Med. Chem. 36, 2689 (1993), using the L1210 murine lymphoid leukemia model.
A human or animal body in need thereof may thus be treated by a method which comprises the administration thereto of a pharmaceutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.
The present invention further provides pharmaceutical compositions comprising a camptothecin derivative of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, as an active principle, in association with one or more Pharmaceutically acceptable carriers and/or diluents.
These pharmaceutical compositions may contain any quantity of a camptothecin derivative of formula (I) which is effective to exhibit any antitumor activity in vivo. Typical in vivo doses are from 0.1 to 60 mg of camptothecin derivative per kg of body weight. A particularly preferred range is from 1 to 40 mg/kg.
The camptothecin derivatives of the present invention may also be mixed with other active materials which do not impair the desired action and/or supplement the desired action.
The pharmaceutical compositions of the present invention may be administered by any route, for example, orally, parenterally, intravenously, intradermally, subcutaneously, or topically, in liquid or solid form. A preferred mode of administration is orally. Oral compositions will generally include an inert diluent or an edible carrier. They may be enclosed in gelatin capsules or compressed into tablets. For the purpose of oral therapeutic administration, The compounds of the present invention may be incorporated with excipients and used in the form of tablets, capsules, elixirs, syrups and the like. These preparations should contain at least 0.1% of active compound but may be varied depending upon the particular form.
The tablets, pills, capsules, troches and the like may contain the following ingredients: a binder such as microcrystalline cellulose, gumtragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, corn starch and the like; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin or flavouring agent such as peppermint, methyl salicylate, or orange flavouring may be added. When the dosage unit form is a capsule, it may contain, in addition to material of the above type, a liquid carrier such as fatty oil. Other dosage unit forms may contain other various materials which modify the physical form of the dosage unit, for example, as coatings. Thus tablets or pills may be coated with sugar shellac, or other enteric coating agents.
A syrup may contain, in addition to the active compounds, sucrose as a sweetening agent and certain preservatives, dyes and colouring and flavours.
Material used in preparing these various compositions should be pharmaceutically pure and non toxic in the amount used. For the purpose of parenteral therapeutic administration, the active ingredient may be incorporated into a solution or suspension.
The solutions or suspensions may also Include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulphite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic.
The dosage values will vary with the specific severity of the disease condition to be alleviated. Good results are achieved when the compounds described herein are administered to a subject requiring such treatment as an effective oral, parenteral or intravenous dose. It is to be understood that for any particular subject, specific dosage regimens should be adjusted to the individual need and the professional judgment of the person administering or supervising the administration of the aforesaid compound. It is to be further understood that the dosages set :forth herein are exemplary only and they do not limit the scope or practice of the invention. The dosages may be administered at once, or may be divided into a number of smaller doses to be administered at varying intervals of time.